The present invention relates generally to a reactive force generation device which generates a reactive force by being depressed to elastically deform in response to an operation of a manual operator that is operable with a hand, foot or other body part of a user (or human operator).
Heretofore, there have been known reactive force generation devices which generate a reactive force by being depressed to elastically deform in response to a user's operation of a manual operator. For example, in the field of electronic keyboard musical instruments, a musical instrument has been known which includes, inside an elastic protrusion protruding from a base plate surface, a dome section protruding toward the base plate surface and a switch that elastically deforms by being depressed by a member, such as a key (see, for example, Japanese Patent Application Laid-open Publication No. 2007-25576 and U.S. Pat. No. 7,256,359 corresponding to the Japanese Patent Application Laid-open Publication No. 2007-25576). In this type of musical instrument, a movable contact is provided at the distal end of the dome section, while a fixed contact is provided on the base plate so that a sensor is turned on by the distal end of the dome section contacting the base plate. A reactive force acting substantially against the key is generated by the dome section and the like elastically deforming in response to depression of the key.
Also known in the art is a reactive force generation device which employs, mainly for the purpose of generating a reactive force, an elastic member included in such a dome section (see, for example, Japanese Patent Application Laid-open Publication No. 2015-68967 and U.S. Pat. No. 9,269,336 corresponding to the No. 2015-68967 publication). In the reactive force generation device disclosed in this patent literature, by a depressing force being applied to the dome section (reactive force generation member) in an axial direction of the dome section, the elastic member of the dome section elastically deforms to generate a reactive force to the applied depressing force. The reactive force thus generated increases as an amount of the elastic deformation increases in response to an increase of the applied depressing force, but, after the generated reactive force reaches its peak, the elastic member of the dome section buckles (i.e., bucklingly deforms) so that the reactive force suddenly decreases. Further, in this known reactive force generation device, the dome section (reactive force generation member) and a depressing section for depressing the doe section are constructed in such a manner that an axis line of the dome section (reactive force generation member) exists within an angle range between a normal line of the depressing surface of the depressing section relative to the dome section at a time point at a time point when the depressing section starts contacting the dome section and a normal line of the depressing surface of the depressing section relative to the dome section at a time point when the depressing section finishes depressing the dome section.
However, if an inclination of the axis line of the dome section relative to a normal line of the base plate surface becomes too great when the distal end of the dome section starts contacting (landing on) an opposed surface, such as the base plate surface, the landing action tends to become unstable. Consequently, an intensity and generation timing of the reactive force would become unstable, and durability of the reactive force generation device too would deteriorate. Further, if depression of the key is detected by electric or electronic contacts provided on respective contacting portions of the opposed surface and the dome section, behavior of the electrical or electronic contacts tend to become unstable, resulting in unwanted chattering so that generation of a sound (tone) may be performed inappropriately. Furthermore, the above-discussed conventionally-known reactive force generation devices are constructed only in consideration of a single-pivot-axis design where a movement (stroke movement) for applying a depressing force to the dome section (reactive force generation member) is made always about a fixed pivot axis; namely, in these conventionally-known reactive force generation device, no consideration is made at all of a complicated stroke movement where the movement for applying a depressing force to the dome section is made about a plurality of pivot axis or about a single pivot axis moving in position.